Facts About Sponges

By Albert Hart.

Sponges belong to the animal kingdom, and the principal varieties used
commercially are obtained off the coasts of Florida and the West Indies;
the higher grades are from the Mediterranean Sea, and are numerous in
variety.

A sponge in its natural state is a different-looking object from what we
see in commerce, resembling somewhat the appearance of the jelly fish,
or a mass of liver, the entire surface being covered with a thin, slimy
skin, usually of a dark color, and perforated to correspond with the
apertures of the canals commonly called holes of the sponge. The
sponge of commerce is, in reality, only the skeleton of a sponge. The
composition of this skeleton varies in the different kinds of sponges,
but in the commercial grades it consists of interwoven horny fibers,
among and supporting which are epiculae of silicious matter in greater
or less numbers, and having a variety of forms. The fibers consist of a
network of fibriles, whose softness and elasticity determine the
commercial quality of a given sponge. The horny framework is perforated
externally by very minute pores, and by a less number of larger
openings. These are parts of an interesting double canal system, an
external and an internal, or a centripetal and a centrifugal. At the
smaller openings on the sponge's surface channels begin, which lead into
dilated spaces. In these, in turn, channels arise, which eventually
terminate in the large openings. Through these channels or canals
definite currents are constantly maintained, which are essential to the
life of the sponge. The currents enter through the small apertures and
emerge through the large ones.

The active part of the sponge, that is, the part concerned in nutrition
and growth, is a soft, fleshy mass, partly filling the meshes and lining
the canals. It consists largely of cells having different functions;
some utilized in the formation of the framework, some in digestion and
others in reproduction. Lining the dilated spaces into which different
canals lead are cells surmounted by whip-like processes. The motion of
these processes produces and maintains the water currents, which carry
the minute food products to the digestive cells in the same cavities.
Sponges multiply by the union of sexual product. Certain cells of the
fleshy pulp assume the character of ova, and others that of spermatozoa.
Fertilization takes place within the sponge. The fertilized eggs, which
are called larvae, pass out into the currents of the water, and, in the
course of twenty-four to forty-eight hours, they settle and become
attached to rocks and other hard substances, and in time develop into
mature sponges. The depth of the water in which sponges grow varies from
10 to 50 feet in Florida, but considerably more in the Mediterranean
Sea, the finer grades being found in the deepest water, having a
temperature of 50 to 57 degrees.